Highly efficient H2 production and size-selective AgCl synthesis via electrolytic cell design

Abstract

Electrosynthesis of chemicals in parallel with hydrogen production exhibits distinct advantages: energy saving and generation of two value-added products. In this work, we first design an asymmetric neutral–acidic electrolytic cell by coupling the silver oxidation reaction (AOR) in a neutral anode chamber with the hydrogen evolution reaction (HER) in an acid cathode chamber. When the anode electrolyte contains a certain amount of chloride ions, AgCl particles can be steadily synthesized close to, but not in contact with, the silver electrode at a fixed voltage. This electrolytic cell requires a voltage of only 1.1 V to drive 10 mA cm⁻². In order to simplify the system and reduce the cost, a symmetric acid membrane-free electrolytic cell is designed; this cell requires a voltage of only 0.95 V to drive 10 mA cm⁻² and 1.37 V to drive 250 mA cm⁻² when a silver rod and graphite rod are used as the anode and cathode, respectively. Besides high purity H₂ generation at the cathode, the anode product is pure AgCl and its size can be controlled by changing the voltage. The Faraday efficiency is close to 95% for both H₂ and AgCl generation.